Relief valve

ABSTRACT

A relief valve includes a cylindrical valve housing attached to an engine body continuously with a relief passage and an outlet provided in an axially intermediate portion thereof. A valve body is slidably fitted to the valve housing so as to allow the relief passage to communicate with the outlet as an oil pressure in the relief passage becomes equal to and exceeds a predetermined oil pressure. A skirt includes an upper end portion fixed to the valve housing above the outlet for guiding oil discharged from the outlet downward. The relief valve exerts a reliable defoaming function in response to an increase in the oil discharged from the outlet and an increase in an ejection pressure thereof while avoiding an increase in the size of the skirt. An annular recessed portion is formed on an outer circumference of the intermediate portion of the valve housing below the outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2005-329856 filed on Nov. 15, 2005 the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a relief valve including: a cylindrical valve housing which is attached to an engine body so as to longitudinally extend continuously with a relief passage communicating with an ejection port of an oil pump and provided in the engine body. An outlet is provided in an axially intermediate portion thereof. A valve body is slidably fitted to the valve housing so as to allow the relief passage to communicate with the outlet as an oil pressure in the relief passage becomes equal to and exceeds a predetermined oil pressure. A skirt is formed in an umbrella shape so as to surround the valve housing and has an upper end portion fixed to the valve housing above the outlet in order to guide oil discharged from the outlet downwardly.

2. Description of Background Art

A relief valve is known, for example, in Japanese Patent Application No. 2001-207818, in which a valve housing is covered with an umbrella-like skirt below an outlet of the valve housing in order to prevent bubbles from being generated when oil discharged from the outlet is returned into an oil reservoir formed in a lower portion of an engine body.

Since it is required that an internal combustion engine be compact, it is not easy to change an inclination angle and size of the skirt so as to increase a flow passage area between the valve housing and the skirt in order to exert a reliable defoaming function in response to an increase in an amount of the oil discharged from the outlet of the relief valve and also to an increase in an ejection pressure thereof.

SUMMARY AND OBJECTS OF THE INVENTION

Tlt is an object of the present invention to provide a relief valve adapted to be capable of exerting a reliable defoaming function in response to an increase in the amount of oil discharged from the outlet and also to the increase of the ejection pressure thereof while avoiding a size increase of the skirt shape.

According to an embodiment of the present invention, a relief valve includes a cylindrical valve housing which is attached to an engine body so as to longitudinally extend continuously with a relief passage communicating with an ejection port of an oil pump and being provided in the engine body. An outlet is provided in an axially intermediate portion thereof. A valve body is slidably fitted to the valve housing so as to allow the relief passage to communicate with the outlet in response to oil pressure in the relief passage becoming equal to and exceeding a predetermined oil pressure. A skirt is provided which is formed in an umbrella shape so as to surround the valve housing and has an upper end portion fixed to the valve housing above the outlet in order to guide oil discharged from the outlet downward. An annular recessed portion is formed on an outer circumference of the intermediate portion of the valve housing below the outlet.

According to an embodiment of the present invention, a lower end of the skirt is disposed at a position corresponding to the intermediate portion of the annular recessed portion.

According to an embodiment of the present invention, an upper end portion of the valve housing, the upper end portion forming an inlet, is fluid-tightly fitted to the relief passage, and a receiving portion for receiving a lower end of the valve housing is provided in the engine body.

In accordance with an embodiment of the present invention, the annular recessed portion is formed on the outer circumference of the intermediate portion of the valve housing. Thus, a size increase of the shape of the skirt can be avoided, a flow passage area between the valve housing and the skirt can be increased, and a reliable defoaming function can be exerted in response to an increase in an amount of oil discharged from the outlet and also to an increase of an ejection pressure thereof. In addition, the annular recessed portion is formed on the outer circumference of the intermediate portion of the valve housing below the outlet, and a high pressure on the relief passage side is not applied to the valve housing below the outlet. Accordingly, the forming of the annular recessed portion does not damage the strength of the valve housing, thus making it possible to contribute to a weight reduction of the relief valve.

Moreover, in accordance with an embodiment of the present invention, the discharged oil which flows between the valve housing and the skirt can be guided by a lower end of the annular recessed portion, and can be discharged so as to spread radially. Thus, a defoaming effect can be enhanced.

Furthermore, in accordance with an embodiment of the present invention, the valve housing is thrust downward by a liquid pressure of the relief passage and the annular recessed portion is formed on the intermediate portion of the valve housing. Accordingly, a seated area of the lower end of the valve housing on the receiving portion provided in the engine body can be set relatively large while increasing a flow passage area between the valve housing and the skirt. Thus, a large load can be avoided from being concentratedly applied to the lower end of the valve housing and the valve housing can be reliably attached to the engine body.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a side view of an internal combustion engine;

FIG. 2 is an enlarged longitudinal cross-sectional side view of main portions of FIG. 1; and

FIG. 3 is a cross-sectional view along a line 3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be made below of a mode for carrying out the present invention based on an embodiment of the present invention, which is shown in the accompanying drawings.

As illustrated in FIG. 1, an engine body 5 includes a cylinder axis inclined upwardly to the front that is mounted on a vehicle body frame of a motorcycle. The engine body 5 includes a cylinder block 8 integrally having a cylinder barrel 6 and an upper case 7 continuous with a lower portion of the cylinder barrel 6. A lower case 9 is coupled to a lower portion of the cylinder block 8 so as to construct a crankcase 10 in cooperation with the upper case 7. An oil pan 11 is coupled to a lower portion of the lower case 9, that is, to a lower portion of the crankcase 10. A cylinder head 12 is coupled to an upper portion of the cylinder block 8 with a head cover 13 coupled to an upper portion of the cylinder head 12. A coupling surface 14 between the upper case 7 and the lower case 9 is set so as to be inclined downwardly to the front in a state where the engine 5 is mounted on the motorcycle.

Between the upper case 7 and the lower case 9, which form the crankcase 10, a crankshaft 15 is provided that includes an axis that is rotatably supported along a vehicle width direction of the motorcycle. To the crankshaft 15, rotational power from a starter motor 16 attached to the upper case 7 is inputted through a starter gear transmission mechanism 17.

An output of the crankshaft 15 is shifted by a gear transmission 18 and is transmitted to a rear wheel as a driving wheel. The transmission 18 is composed by providing gear trains between a main shaft 19 and a counter shaft 20. The gear trains are capable of selectively establishing a plurality of speeds. The main shaft 19 has an axis parallel to the crank shaft 15, and is rotatably supported between the upper case 7 and the lower case 9. The counter shaft 20 has an axis parallel to the main shaft 19, and is rotatably supported by the lower case 9.

Onto one end of the main shaft 19, a starting clutch 21 interposed between the crankshaft 15 and the main shaft 19 is attached. When the starting clutch 21 turns to an engaged state in response to a shifting operation of a rider, power from the crankshaft 15 is transmitted to the main shaft 19.

Between the cylinder head 12 and the head cover 13, a valve mechanism 24 including an intake camshaft 22 and an exhaust camshaft 23 is housed. To the intake camshaft 22 and the exhaust camshaft 23, which are supported rotatably by the cylinder head 12, the rotational power of the crankshaft 15 is transmitted, which is reduced by half in speed by the timing transmission means 26 including a timing chain 25.

Referring to FIG. 2 in combination, to the lower case 9 in the crankcase 10, an oil pump 28 having a rotation axis parallel to the crankshaft 15 is attached. An endless chain 32 is wound around a drive sprocket 31 fixed to the main shaft 19 of the gear transmission 18, and around a driven sprocket 30 fixed to a rotation shaft 29 of the oil pump 28.

Oil reserved in an oil reservoir 33 formed in the oil pan 11 is drawn up by the oil pump 28 through an oil strainer 34. In the lower case 9, an ejection passage 35 that extends parallel to the coupling surface 14 between the upper case 7 and the lower case 9 is provided so as to communicate with an ejection port 36 of the oil pump 28. Thus, oil from the oil pump 28 is ejected to the ejection passage 35. In addition, a relief passage 37 which is perpendicularly branched from the ejection passage 35 extends downwardly so as to allow an upper end portion thereof to communicate with the ejection passage 35 provided in the lower case 9. By a function of a relief valve 38 connected to the relief passage 37, the pressure of the oil in the ejection passage 35 is maintained to be constant.

In addition, to lubricated portions of the engine body 5, such as between crank journal walls 39 . . . and the crankshaft 15, which the crankcase 10 includes, the oil is supplied from a main gallery 40 provided in the lower case 9 of the crankcase 10. The main gallery 40 is connected to the ejection passage 35 through an oil filter 41 and an oil cooler 42.

More specifically, the oil ejected from the oil pump 28 is pressure-regulated by the relief valve 38, and as shown by arrows in FIG. 2, is cleaned by the oil filter 41, is then cooled by the oil cooler 42, and is guided to the main gallery 40.

Referring to FIG. 3 in combination, the relief valve 38 includes a cylindrical valve housing 44 which is attached between the lower case 9 and oil pan 11 of the engine body 5 so as to longitudinally extend continuously with the relief passage 37 and includes outlets 43 . . . provided in axially intermediate portions thereof. A valve body 45 is slidably fitted to the valve housing 44 so as to allow the relief passage 37 to communicate with the outlets 43 . . . as the oil pressure in the relief passage 37 becomes equal to and exceeds a predetermined oil pressure. A skirt 46 is formed in an umbrella shape in a portion surrounding the outlets 43 . . . and has an upper end portion fixed to the valve housing 44 above the outlets 43 . . . in order to guide the oil discharged from the outlets 43 . . . downward.

The relief passage 37 is provided in the lower case 9 so as to longitudinally extend so that a lower end thereof opens to the oil reservoir 33 side. An upper end portion of the valve housing 44, which forms an inlet 47, is fluid-tightly fitted to the lower end portion of the relief passage 37 so as to allow the inlet 47 to communicate with the relief passage 37. More specifically, an O-ring 48 is attached to an outer circumference of the valve housing 44 in a fitted portion of the valve housing 44 to the relief passage 37.

In the oil pan 11 in the engine body 5, a receiving portion 49 projects upwardly that receives a lower end of the valve housing 44. The receiving portion 49 is formed into a cylindrical shape so as to longitudinally extend upwardly. Since the coupling surface 14 between the upper case 7 and the lower case 9 is inclined downwardly to the front, and the valve housing 44 coaxially continues with the relief passage 37 perpendicularly branched from the ejection passage 35 extending parallel to the coupling surface 14. An upper end surface of the receiving portion 49 is formed in an inclined manner so as to perpendicularly abut on the lower end of the valve housing 44. In addition, a notch 55 is provided in a part along a circumferential direction of the receiving portion 49.

The outlets 43 . . . are provided on the axially intermediate portions of the valve housing 44 so as to be located below the lower case 9 when the upper end portion of the valve housing 44 is fluid-tightly fitted to the lower case 9 so as to coaxially continue with the relief valve 37. The valve body 45 slidably fitted to the valve housing 44 so as to switch the communication/shutoff between the inlet 47. The outlets 43 . . . are formed into a closed-end cylindrical shape in which an upper end is closed.

In addition, above the outlets 43 . . . , into the valve housing 44, a stopper pin 50 having an axis along one diameter line thereof is inserted. An upper limit position of the valve body 45 is regulated in such a manner that the upper-end closed portion thereof abuts on the stopper pin 50, and the valve body 45 located at the upper limit position makes a shutoff between the inlet 47 and the outlets 43 . . . .

Moreover, a disk-like retainer 52 is inserted into a lower portion of the valve housing 44 so that a downward movement thereof can be regulated by a snap ring 51 attached to an inner surface of the lower end of the valve housing 44. A valve spring 53 which urges the valve body 45 upward is compressed between the retainer 52 and the valve body 45. Then, when a force in a valve opening direction, which presses the valve body 45 downward by the oil pressure in the inlet 47 communicating with the relief passage 37, exceeds a force in a valve closing direction, which urges the valve body 45 upwardly by the valve spring 53, the valve body 45 moves downwardly so as to allow the inlet 47 to communicate with the outlets 43 . . . . More specifically, the oil pressures in the relief passage 37 and the ejection passage 35 are maintained to be constant by the function of the relief valve 38.

The skirt 46 integrally includes, in order from an upper end thereof a small-diameter cylindrical portion 46 a press-fitted to the valve housing 44, a tapered portion 46 b which allows a small-diameter end thereof to coaxially continue with a lower end of the small-diameter cylindrical portion 46 a and is formed to be larger in diameter as going downward and a large-diameter cylindrical portion 46 c which coaxially continues with a lower end, that is, a large-diameter end of the tapered portion 46 b. The small-diameter cylindrical portion 46 a is fixed to the valve housing 44 by press fitting and the like so as to cover both ends of the stopper pin 50 in order to inhibit the stopper pin 50 from separating from the valve housing 44. The valve housing 44 is surrounded by the tapered portion 46 b and large-diameter cylindrical portion 46 c of the skirt 46, and the tapered portion 46 b and the large-diameter cylindrical portion 46 c form the umbrella shape surrounding the valve housing 44.

In addition, an annular recessed portion 54 is formed on an outer circumference of the intermediate portion of the valve housing 44 below the outlets 43 . . . . A lower end of the skirt 46, that is, a lower end of the large-diameter cylindrical portion 46 c is disposed at a position corresponding to the intermediate portion of the annular recessed portion 54.

Next, a description will be made of functions of this embodiment. In order to prevent bubbles from being generated when the oil discharged from the outlets 43 . . . provided in the valve housing 44 of the relief valve 38 is returned into the oil reservoir 33 in the oil pan 11, the upper end portion of the skirt 46 formed into the umbrella shape so as to surround the outlets 43 . . . is fixed to the valve housing 44 above the outlets 43 . . . . Moreover, the annular recessed portion 54 is formed on the outer circumference of the intermediate portion of the valve housing 44 below the outlets 43 . . . . Therefore, it is possible to avoid a size increase of the shape of the skirt 46 and to increase a flow passage area between the outlets 43 . . . and the skirt 46. Thus, a reliable defoaming function can be exerted in response to an increase in an amount of the oil discharged from the outlets 43 . . . and also to an increase in an ejection pressure thereof. In addition, the annular recessed portion 54 is formed on the outer circumference of the intermediate portion of the valve housing 44 below the outlets 43 . . . , and a high pressure on the relief passage 37 side is not applied to the valve housing 44 below the outlets 43 . . . . Accordingly, the forming of the annular recessed portion 54 does not damage the strength of the valve housing 44. Thus, it is possible to reduce the weight of the relief valve 38.

Moreover, the lower end of the skirt 46 is disposed at the position corresponding to the intermediate portion of the annular recessed portion 54. Accordingly, the discharged oil which flows between the valve housing 44 and the skirt 46 can be guided by the lower end of the annular recessed portion 54, and can be discharged so as to spread radially, and a defoaming effect can be enhanced.

Moreover, the upper end portion of the valve housing 44, which forms the inlet 47, is fluid-tightly fitted to the relief passage 37, the receiving portion 49 which receives the lower end of the valve housing 44 is provided in the oil pan 11, and the valve housing 44 is thrust on the receiving portion 49 side by the liquid pressure of the relief passage 37. Furthermore, the annular recessed portion 54 is formed on the intermediate portion of the valve housing 44. Accordingly, a seated area of the lower end of the valve housing 49 on the receiving portion 49 can be set relatively large while increasing a flow passage area between the valve housing 44 and the skirt 46. Thus, a large load can be avoided from being concentratedly applied to the lower end of the valve housing 44, and the valve housing 44 can be reliably attached to the engine body 5.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. 

1. A relief valve comprising: a cylindrical valve housing attached to an engine body and longitudinally extending continuously with a relief passage for communicating with an ejection port of an oil pump which is provided in the engine body, said cylindrical valve housing being provided with an outlet in an axially intermediate portion thereof; a valve body slidably fitted relative to the valve housing to allow the relief passage to communicate with the outlet as oil pressure in the relief passage becomes equal to and exceeds a predetermined oil pressure; a skirt formed in an umbrella shape to surround the valve housing with an upper end portion of the skirt being fixed to the valve housing above the outlet in order to guide oil discharged from the outlet downward; and an annular recessed portion being formed on an outer circumference of the intermediate portion of the valve housing below the outlet.
 2. The relief valve according to claim 1, wherein a lower end of the skirt is disposed at a position corresponding to an intermediate portion of the annular recessed portion.
 3. The relief valve according to claim 1, wherein an upper end portion of the valve housing, the upper end portion forming an inlet, is fluid-tightly fitted to the relief passage and a receiving portion for receiving a lower end of the valve housing.
 4. The relief valve according to claim 2, wherein an upper end portion of the valve housing, the upper end portion forming an inlet, is fluid-tightly fitted to the relief passage and a receiving portion for receiving a lower end of the valve housing.
 5. The relief valve according to claim 1, wherein the skirt is an annular member that extends along the valve housing a predetermined distance for covering the outlet while being spaced apart a predetermined distance therefrom.
 6. The relief valve according to claim 3, and further including a sealing ring for providing a fluid-tight fit for the upper portion of the inlet to said relief passage.
 7. The relief valve according to claim 1, and further including a biasing means operatively connected to said valve body for normally biasing said valve body to a position for closing said outlet.
 8. The relief valve according to claim 1, and further including a stopper pin operatively positioned within said valve housing for limiting the movement of the valve body when the valve body closes the outlet.
 9. The relief valve according to claim 7, wherein the outlet is opened when the oil pressure in the relief passage is greater than the biasing force of said biasing means acting on said valve body.
 10. The relief valve according to claim 1, wherein the size of the skirt surrounding the outlet is formed for increasing the flow passage area between the outlet and the skirt for ensuring defoaming of the oil.
 11. A relief valve comprising: a valve housing longitudinally extending continuously with a relief passage for communicating with an ejection port of an oil pump, said valve housing being provided with an outlet in an axially intermediate portion thereof; a valve body slidably fitted relative to the valve housing to allow the relief passage to communicate with the outlet as oil pressure in the relief passage becomes equal to and exceeds a predetermined oil pressure; a skirt formed to surround the valve housing with an upper end portion of the skirt being fixed to the valve housing above the outlet in order to guide oil discharged from the outlet downwardly; and an recessed portion being formed on an outer circumference of the intermediate portion of the valve housing below the outlet.
 12. The relief valve according to claim 11, wherein a lower end of the skirt is disposed at a position corresponding to an intermediate portion of the annular recessed portion.
 13. The relief valve according to claim 11, wherein an upper end portion of the valve housing, the upper end portion forming an inlet, is fluid-tightly fitted to the relief passage and a receiving portion for receiving a lower end of the valve housing.
 14. The relief valve according to claim 12, wherein an upper end portion of the valve housing, the upper end portion forming an inlet, is fluid-tightly fitted to the relief passage and a receiving portion for receiving a lower end of the valve housing.
 15. The relief valve according to claim 11, wherein the skirt is an annular member that extends along the valve housing a predetermined distance for covering the outlet while being spaced apart a predetermined distance therefrom.
 16. The relief valve according to claim 13, and further including a sealing ring for providing a fluid-tight fit for the upper portion of the inlet to said relief passage.
 17. The relief valve according to claim 11, and further including a biasing means operatively connected to said valve body for normally biasing said valve body to a position for closing said outlet.
 18. The relief valve according to claim 11, and further including a stopper pin operatively positioned within said valve housing for limiting the movement of the valve body when the valve body closes the outlet.
 19. The relief valve according to claim 17, wherein the outlet is opened when the oil pressure in the relief passage is greater than the biasing force of said biasing means acting on said valve body.
 20. The relief valve according to claim 11, wherein the size of the skirt surrounding the outlet is formed for increasing the flow passage area between the outlet and the skirt for ensuring defoaming of the oil. 